[PATCH v7 09/25] arm64: Unmask PMR before going idle

[Julien Thierry]

CPU does not received signals for interrupts with a priority masked by
ICC_PMR_EL1. This means the CPU might not come back from a WFI
instruction.

Make sure ICC_PMR_EL1 does not mask interrupts when doing a WFI.

Since the logic of cpu_do_idle is becoming a bit more complex than just
two instructions, lets turn it from ASM to C.

Signed-off-by: Julien Thierry <julien.thierry@xxxxxxx>
Suggested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
 arch/arm64/kernel/process.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 arch/arm64/mm/proc.S        | 11 -----------
 2 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 34f495b..28b7423 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -51,6 +51,7 @@
 #include <linux/thread_info.h>
 
 #include <asm/alternative.h>
+#include <asm/arch_gicv3.h>
 #include <asm/compat.h>
 #include <asm/cacheflush.h>
 #include <asm/exec.h>
@@ -73,6 +74,50 @@
 
 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 
+static inline void __cpu_do_idle(void)
+{
+	dsb(sy);
+	wfi();
+}
+
+static inline void __cpu_do_idle_irqprio(void)
+{
+	unsigned long pmr;
+	unsigned long daif_bits;
+
+	daif_bits = read_sysreg(daif);
+	write_sysreg(daif_bits | PSR_I_BIT, daif);
+
+	/*
+	 * Unmask PMR before going idle to make sure interrupts can
+	 * be raised.
+	 */
+	pmr = gic_read_pmr();
+	gic_write_pmr(GIC_PRIO_IRQON);
+
+	__cpu_do_idle();
+
+	gic_write_pmr(pmr);
+	write_sysreg(daif_bits, daif);
+}
+
+/*
+ *	cpu_do_idle()
+ *
+ *	Idle the processor (wait for interrupt).
+ *
+ *	If the CPU supports priority masking we must do additional work to
+ *	ensure that interrupts are not masked at the PMR (because the core will
+ *	not wake up if we block the wake up signal in the interrupt controller).
+ */
+void cpu_do_idle(void)
+{
+	if (system_uses_irq_prio_masking())
+		__cpu_do_idle_irqprio();
+	else
+		__cpu_do_idle();
+}
+
 /*
  * This is our default idle handler.
  */
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 2c75b0b..2fb822b 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -49,17 +49,6 @@
 
 #define MAIR(attr, mt)	((attr) << ((mt) * 8))
 
-/*
- *	cpu_do_idle()
- *
- *	Idle the processor (wait for interrupt).
- */
-ENTRY(cpu_do_idle)
-	dsb	sy				// WFI may enter a low-power mode
-	wfi
-	ret
-ENDPROC(cpu_do_idle)
-
 #ifdef CONFIG_CPU_PM
 /**
  * cpu_do_suspend - save CPU registers context
-- 
1.9.1